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<?php var_dump( array_udiff( [$a = new \stdClass, $b = new \stdClass], [$c = new \stdClass, $b], function ($first, $second) { return $first === $second ? 0 : 1; } ) );
Output for 7.0.0 - 7.0.20, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.29, 8.2.0 - 8.2.20, 8.3.0 - 8.3.8
array(1) { [0]=> object(stdClass)#1 (0) { } }
Output for 5.5.0 - 5.5.36, 5.6.0 - 5.6.28
array(2) { [0]=> object(stdClass)#1 (0) { } [1]=> object(stdClass)#2 (0) { } }

preferences:
148.06 ms | 402 KiB | 267 Q